Field Area Routers (FARs) are routers in a computer network (e.g., a Smart Grid) that are installed in the field at various locations to provide communication between nodes of a local computer network (a field area network or FAN) and a central or wide area network (WAN). For example, on the “southbound,” FARs may connect Low power and Lossy Networks (LLNs) domains that comprise a large number of devices such as sensors and actuators using low power shared-media links, such as wireless or powerline communication (PLC) links. On the “northbound,” FARs communicate with the Utility Control Center using various wireless backhaul technologies such as 2G, 3G, LTE, WiMax, etc., as will be understood by those skilled in the art. In other words, FARs often act as “root nodes” through which all of the traffic transits between the local network to a control center, and thus play a critical role in the network infrastructure.
In a typical field area network, such as one configured for Advanced Metering Infrastructure (AMI) applications, a FAR may communicate with thousands of end-points (nodes) on the downlinks (access network) using an IP-based mesh network. The nodes themselves, which may be stationary nodes, may actually connect to one or more FARs depending on various factors such as their proximity, available signal strength, interference, availability of suitable neighbors, etc. In some areas, these factors change very often, and what has been observed in deployed networks is that as many as 35% of the nodes migrate (roam) to adjoining FARs on a daily basis.
A mesh network is typically secured using group-based encryption keys and these keys are initially forwarded to the mesh nodes using a known authentication scheme. The process of node authentication and network admission is quite expensive, especially in low bandwidth mesh networks, and the load on the security servers. It has been observed that authentication is a significant component of the time for a node to effectively join a network; a major issue considering that the joining time is a critical component for many service level agreements (SLAs).